Masovia or
Mazovia (
Polish Mazowsze) is a geographic and
historic region situated in eastern
Poland's
Masovian Plain. Its historic capitals include
Plock.
Masovia probably became part of Poland by the reign of Mieszko I in the 10th century, the first historically known Piast duke of the Polans in the 10th century. After the death of Mieszko II in 1034, the local governor Mieclaw supported an anti-Christian rebellion, which was subsequently subdued by Duke Casimir I, Duke of Poland, in 1047 with help from Ruthenian units.
Following the death of Boleslaw III Wrymouth, Poland was divided in duchies, according to his testament (see fragmentation of Poland). After the death of the last Masovian Piast, Janusz III, in 1526, Masovia became a voivodeship of the Kingdom of Poland.
Masovia was annexed by the Kingdom of Prussia during the 18th century Partitions of Poland and briefly administered within South Prussia and New East Prussia. Among others the territory became part of the Duchy of Warsaw in 1807 during the Napoleonic Wars, but was included within Congress Poland, a puppet state of the Russian Empire, in 1815.
